The partial collapse of Cambodia's 120-MW Stung Atay hydropower project has left several workers missing and four presumed to have drowned, HydroWorld.com has learned.

The Stung Atay dam, located in western Cambodia on the Atay River, appears to have failed Saturday after an excessive amount in the reservoir caused a leak in the structure.

Work on the US$225 million project has been halted while various agencies investigate the collapse, Cambodian sources report.

The dam has been a work-in-progress since 2008 and was to have been completed in May 2013. The project is being undertaken by the China Datang Corporation as per a 30-year build-operate-transfer arrangement.